Scientists question badger cull

Scientists have released date suggesting badgers are more likely to spread disease when their social networks are perturbed.

Culling badgers causes disturbances to their social structure that may promote the spread of bovine tuberculosis, say scientists.

A study conducted in England found that TB-infected badgers tended to be shunned within their social groups. They were more isolated than uninfected badgers.

In undisturbed badger communities, this helped to keep the disease confined to a few affected individuals within a group.

But this could change when a social group was disrupted, for instance by culling. In these circumstances, infected animals were likely to spread the disease to other groups.

Dr Robbie McDonald, from the University of Exeter, who led the research reported in the journal Current Biology, said: "This unusual social arrangement may help explain why TB tends not to spread easily in undisturbed badger populations but also may help explain why, when their social networks are perturbed, infection spreads quickly to other badgers and onwards to cattle.

"Just as in humans, social networks are very important for disease transmission. When management changes stable networks, the results for disease control are often counter-intuitive and unexpected."

The scientists studied the social networks of badgers by fitting more than 50 wild animals with electronic "proximity collars" that recorded their interactions.

"This study has revealed an important link between social networks and TB infection," said Prof McDonald. "Infected animals were likely to be less important for spread within groups while at the same time being more important for spread between groups."

The findings suggest that badger management is most effective when it maintains stability and does not disrupt social networks.

"The good news is that vaccination does not disturb social structure," said Prof McDonald. "The sort of social structure we have observed - where relatively few individuals might be responsible for disease spread - lends itself to vaccination and could lead quite rapidly to herd immunity."